This invention relates to a new and improved method and apparatus for moving a signature to a work station, stitching the signature at the work station and moving the stitched signature away from the work station.
A known machine uses a shuttle assembly to move a signature to a stitching station. As soon as the signature is released by the shuttle assembly at the stitching station, the direction of movement of the shuttle assembly is reversed and the shuttle assembly returns to grip the next succeeding signature. After the first signature has been stitched, the next signature is moved to the stitching station by the shuttle assembly. One known machine having this general construction is shown in U.S. Pat. No. 3,554,531.
Although machines of this type have been satisfactory in their operation, difficulty has been encountered in designing and manufacturing a relatively inexpensive machine which is capable of operating satisfactorily at high speeds. Part of this difficulty is due to the relatively large operating forces to which the numerous parts of the shuttle assembly are subjected during high speed reversal of the direction of shuttle movement. Thus each time a signature is moved to the stitching station, the shuttle assembly is moved through a forward stroke, quickly stopped, opened, rapidly moved through a reverse stroke of the same length as the forward stroke and then closed on a next succeeding signature.
Almost half of the operating time of the shuttle assembly is wasted in that it is spent in returning the shuttle assembly from an end of stroke position to a beginning of stroke position. During this return stroke, the shuttle assembly does not do any useful work. However, during the return stroke the numerous components of the shuttle assembly are subjected to wear inducing forces, particularly during rapid acceleration and deceleration of the shuttle assembly.